Nuclear Fuel Guide Pin Attachment for Core Plate Strength
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Solution Overview
Problem
The strength of a core plate in nuclear reactors is compromised when a fuel guide pin is attached, as the lower large diameter portion of the pin can interfere with continuous coolant holes, potentially reducing the plate's structural integrity.
Innovation Solution
A fuel guide pin design featuring a constricted portion between the shrink fit and pin portions, with a smoothly narrowed lower portion, allows for a smaller outer diameter of the shrink fit portion, keeping it spaced from coolant holes, and includes a flange and external threaded ring for enhanced attachment and stress distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lower large diameter portion of the fuel guide pin is made larger to ensure secure attachment to the core plate, then the attachment reliability is improved, but the distance to the continuous coolant holes decreases, compromising the core plate strength
Solution Approach 1:
The fuel guide pin is segmented into distinct portions: an upper pin portion for fuel insertion, a constricted portion with reduced diameter, and a lower shrink fit portion for attachment. This segmentation allows the shrink fit portion to be optimized for attachment while the constricted portion maintains distance from coolant holes, resolving the contradiction between attachment reliability and core plate strength.
Solution Approach 2:
The constricted portion introduces local quality variation by reducing the diameter in a specific region between the pin portion and shrink fit portion. This localized diameter reduction creates sufficient spacing from coolant holes while the shrink fit portion maintains its attachment function, thus preserving both core plate strength and attachment reliability.
2Stability of the object's composition
If the fuel guide pin is embedded deeper into the core plate to ensure secure fixation, then the attachment stability is improved, but the risk of interfering with continuous coolant holes increases, compromising the structural integrity
Solution Approach 1:
The fuel guide pin is divided into functional segments with the constricted portion acting as a spacer. This segmentation enables the shrink fit portion to be positioned at an optimal depth for stable attachment while preventing interference with coolant holes, thus maintaining both attachment stability and structural integrity.
Solution Approach 2:
The constricted portion serves as an intermediary element between the pin portion and shrink fit portion. It provides the necessary spacing to prevent the shrink fit portion from contacting coolant holes while still allowing secure attachment, thereby resolving the conflict between attachment stability and structural integrity.
3Strength
If the outer diameter of the shrink fit portion is reduced to increase spacing from coolant holes, then the core plate strength is improved, but the attachment security may be compromised
Solution Approach 1:
The diameter parameter of the fuel guide pin is varied along its length, with the constricted portion having a reduced diameter. This parameter change allows the shrink fit portion to maintain sufficient spacing from coolant holes for core plate strength while the shrink fit mechanism ensures secure attachment, thus resolving the contradiction between strength and reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enables the fuel guide pin to be securely embedded in the core plate without passing through it, maintaining the plate's strength and ensuring reliable attachment, even with large plate thicknesses.
Implementation Method 1
a shrink fit portion (2) inserted into a recessed portion (22a) provided in a lower core support plate (22) and fixed to the lower core support plate (22) by shrink fit
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A fuel guide pin to be fixed to a core plate includes a shrink fit portion (2) which is inserted into a recessed portion (22a) having a bottom and being provided in a core support plate (22) and fixed thereto by means of shrink fit; a pin portion (3) provided above the shrink fit portion (2) and projecting from an upper surface of the core support plate (22), over which a fuel assembly to be loaded on the core support plate (22) is inserted; and a constricted portion (4) which is provided between the shrink fit portion (2) and the pin portion (3) in a constricted shape having a smaller diameter than an outer diameter of the pin portion (3) and has a lower narrowed portion (4) a smoothly narrowed toward the most constricted portion from the shrink fit portion side (2).